Disclaimer #2: I am also not a real blogger. I wrote this in Word, and it took me a few days to get it as simple as possible, but I had font issues with copying & pasting it. Sorry that some parts have abrupt font changes. I don't know enough html coding to fix it.
Over the past few weeks, I’ve learned a lot about ears, hearing, and data analysis. Now I’m going to share it all, so saddle up for some scientific good times J
First things first, here’s a brief education in Pediatric Audiology. I present to you: the ear.
As you can see, the ear has three zones---outer, middle, and inner. Sound waves travel into the outer ear and cause the ear drum to vibrate, which causes the “three ear bones” to vibrate. Those vibrations then travel through the cohlea (the snail-shaped thing in the inner ear) and the cells in the cochlea send information through the auditory nerve to the brain, which tells you what you are hearing.
There are 2 families of causes of hearing loss. The first is conductive, meaning that the sound does not get properly "conducted" from the outer ear all the way to the nerve in the back of the ear system, due to a myriad of issues that could arise anywhere along the pathway. (This is common in children who might have fluid in the middle ear, ear infections, etc). The second source of hearing loss is sensorineural, meaning the the sound can be conducted through the system properly, but there is a disruption along the neural pathway.
The goal of hearing testing is to figure out the softest level that a child can detect each of the different pitches (so if your data line was right up near the top, you would have great hearing . . . if you were at the bottom, profound hearing loss.)
The other color-coded zone on the audiogram is that blue/grey “speech banana”. The speech banana is represents the volumes and pitches of average conversational speech (if you want to get more technical, it represents the average conversational pitches and volumes of 2 people with normal hearing talking at about 5-7 feet apart).
Here, the child’s hearing thresholds are within the speech banana. That suggests that she has access to the sounds necessary to develop spoken language. A child with this type of hearing loss could still responds well when spoken to, even from another room, like Maya does. However, this speech may sound much softer to her, and if there is background noise it would become difficult for her to hear and understand conversational speech.
But here’s what’s really interesting. Maya’s hearing loss follows a loosely similar pattern to this made-up data, in that her hearing loss is slightly more pronounced at high frequencies. When we heard that her impairment was more significant at higher pitches, we thought “Well, what’s high pitched? Dog whistles, microwaves beeping?” What we didn’t know what that every speech sound has its own frequency. Check out the letters on the audiogram . . . you can see that the j-m-d sounds are low pitched, p-h-g are in the middle, and f-s-th are high pitched.
I’m also rethinking some of her oral-motor issues. If I say, “Maya, say ‘dada’” and she replies “Baba!” is that because she couldn’t get her mouth organized enough to say “dada” or because she misheard me?
I almost cancelled the ABR when I realized a few days beforehand that I can stand in the kitchen and say “What does a ‘B’ say?” and Maya can respond from the living room “Ba!”. I thought, surely, if she can hear that I said B (instead of D or P) from a room away, without seeing my lips move, then her hearing must be fine. But it’s not.
Make sure that you are working with an ENT that you trust, and explore the possibility of hearing impairment. Every time our ENT said “Oh, has it been 6 months? Let’s get her in for the behavioral hearing eval again.” I would roll my eyes and dread the appointment---which typically ended with a breakdown (on Maya’s part) and frustration (at spending our time in another appointment that yielded not much information). But thank goodness we all stuck with it.